Dihydroartemisinin alleviates ammonia toxicity and autophagy in zebrafish (Danio rerio) gill

Ammonia is highly toxic to aquatic organisms and has become a consistent pollutant in intensive fish farming conditions. Dihydroartemisinin (DhA) has potential value in the treatment of ammonia poisoning in aquaculture. However, the application investigation of DhA is insufficient in the field of aquaculture. In the present study, 540 zebrafish with an average body weight of (1.00 ± 0.01) g were randomly assigned into 9 groups. The zebrafish were fed a basal diet supplemented with or without 0.25% or 0.5% DhA for 1 week. The zebrafish were then exposed to water supplemented with or without 40 or 80 mg/L ammonium acetate (NH₄AC) for 4 days. The results showed that dietary supplementation with 0.5% DhA attenuated mortality and ammonia accumulation in zebrafish exposed to 80 mg/L NH₄AC. In addition, the alleviative effects of 0.5% DhA were associated with enhanced mRNA levels for ammonia transporter (Rhesus-associated glycoprotein, Rh family C glycoprotein 1, Na⁺/K⁺-ATPase, carbonic anhydrase), anti-inflammatory cytokines (transforming growth factor β), as well as the down-regulation of mRNA expression of inflammatory factors (interleukin 1β), hypoxia-inducible factors (hypoxia-inducible factor 1 αb, hypoxia-inducible factor 2α), and protein abundances of autophagy (autophagy-related gene 5, BCL-2-interacting myosin-like coiled-coil protein-1, microtubule-associated protein 1 light chain 3 Ⅱ, cathepsin B, cathepsin L). Taken together, DhA has great potential in aquaculture as a defence against ammonia toxicity.